• Wind and Structures
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• v.34 no.1
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• pp.43-58
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• 2022

The BARC flow is studied via Direct Numerical Simulation at a relatively low turbulent Reynolds number, with focus on the geometrical representation of the leading-edge (LE) corners. The study contributes to further our understanding of the discrepancies between existing numerical and experimental BARC data. In a first part, rounded LE corners with small curvature radii are considered. Results show that a small amount of rounding does not lead to abrupt changes of the mean fields, but that the effects increase with the curvature radius. The shear layer separates from the rounded LE at a lower angle, which reduces the size of the main recirculating region over the cylinder side. In contrast, the longitudinal size of the recirculating region behind the trailing edge (TE) increases, as the TE shear layer is accelerated. The effect of the curvature radii on the turbulent kinetic energy and on its production, dissipation and transport are addressed. The present results should be contrasted with the recent work of Rocchio et al. (2020), who found via implicit Large-Eddy Simulations at larger Reynolds numbers that even a small curvature radius leads to significant changes of the mean flow. In a second part, the LE corners are fully sharp and the exact analytical solution of the Stokes problem in the neighbourhood of the corners is used to locally restore the solution accuracy degraded by the singularity. Changes in the mean flow reveal that the analytical correction leads to streamlines that better follow the corners. The flow separates from the LE with a lower angle, resulting in a slightly smaller recirculating region. The corner-correction approach is valuable in general, and is expected to help developing high-quality numerical simulations at the high Reynolds numbers typical of the experiments with reasonable meshing requirements.

• Research in Community and Public Health Nursing
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• v.33 no.3
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• pp.290-298
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• 2022

Purpose: This study was conducted to determine factors influencing changes in the self-esteem of multicultural adolescents over time. Methods: A longitudinal design was adopted to analyze secondary data. This study used the 2nd, 4th, and 6th year data of Multicultural Adolescents Panel Study (MAPS) collected by the Korea Youth Policy Institute. The linear mixed model was utilized to analyze self-esteem changes over time. Results: The factors of sex and age of the students, the mother's Korean writing ability, and the Filipino or Japanese mothers had a significant effect on the self-esteem change of multi-cultural adolescents over time. Specifically, it was found that female students' self-esteem was decreased by 0.04 (t=-2.39, p=.017) more than male students over time. As the subject's age and mother's Korean writing ability increased, self-esteem was decreased by 0.01 (t=-2.53, p=.011) and 0.03 (t=-2.52, p=.012) over time. In addition, compared to that of those who had mothers from Korea, self-esteem of those who had Filipino or Japanese mothers was decreased by 0.04 significantly. Conclusion: Therefore, when developing a self-esteem promotion program, it is necessary to develop content by reflecting the characteristics of mothers as well as the gender and age of students. Furthermore, the significance of this study is in that it established a foundation for a positive self-identity of multicultural adolescents whose number is increasing recently by identifying factors affecting their self-esteem.

• Journal of Digital Convergence
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• v.20 no.3
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• pp.517-527
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• 2022

This study aimed to compare changes in cognitive function, depression and ability to perform activity of daily living (ADL) in patients with dementia, mild cognitive impairment (MCI), and ischemic stroke (IS) and to identify factors associated with changes in instrumental ADL. A total of 86 patients (dementia=30, MCI=32, and IS=24) were included to analyse cognitive function, depression, and basic and instrumental ADL obtained at the time of diagnosis and 1 year after baseline. Repeated measures analysis of variance and multiple linear regression were used. A significant group by time interaction was found in executive function (p=.037) and instrumental ADL (p=.023) across groups. The MCI group has little change in executive function and instrumental ADL from the baseline to 1 year after diagnosis while other two groups showed changes with the dementia group showing declines and the group of IS having improvement in these factors over time. Changes in executive function(p=.030) and basic ADL (p<.001) explained 26.9% in the variance of changes in instrumental ADL. These findings showed a different changing pattern in executive function during the first year after diagnosis of dementia, MCI, and IS which have cognitive changes as their main symptoms, probably leading to a different changing pattern in instrumental ADL. Healthcare professionals should routinely assess for executive function and instrumental ADL problems and intervene to maintain and improve these functional outcomes immediately after disease.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.81-91
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• 2011

This study was conducted to evaluate the necessity of the anchor lug system in continuously reinforced concrete pavement(CRCP) by comparing longitudinal displacements of CRCPs with and without anchor lugs, and to investigate the effect of horizontal cracking on CRCP performance by measuring the vertical displacements. The measurements before and after the anchor lug section was separated were conducted for 12 days in June, and for 14 days in August after the abrupt displacements according to cutting disappeared, respectively. This short term measurement results showed that when anchor lugs were installed, a daily displacement variation at any location was less than 0.1mm; therefore, longitudinal movements were negligibly small. When there were no anchor lugs, longitudinal displacements mainly occurred near the free end and the displacement variation was small; therefore, an expansion joint system seems to be employed at a CRCP terminus without installing anchor lugs. However, further studies are needed to verify the terminus behavior due to annual temperature changes. The horizontal crack width variation was ignorable and did not affect the vertical displacement of the slab. Therefore, the horizontal crack did not delaminate the slab and did not seem to reduce the structural capacity and performance of CRCP.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.293-302
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• 2016

The study explores how academic strain, unhappiness, and mobile phone dependency among adolescents have changed over time. And we conducted the longitudinal and complex analysis on the influence of academic strain on unhappiness and mobile phone dependency in order to search the ways to prevent a vicious circle among them. We used general strain theory as a conceptual research frame and analysed the data of 1,589 respondents of the 2nd~4th Korean Children and Youth Panel with latent growth modeling. It was found that the levels of academic strain, unhappiness, and mobile phone dependency among adolescents were linearly increased across time. Academic strain initial status positively affected unhappiness initial status and both the initial status and change rate of mobile phone dependency. The change rate of unhappiness positively affected that of mobile phone dependency. Academic strain change rate positively influenced that of mobile phone dependency mediated by unhappiness change rate. We provided useful implications to academic activities, negative emotions, and mobile phone dependency for adolescents and suggested future studies about reasons of the changes of those variables.

• Journal of Convergence for Information Technology
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• v.9 no.12
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• pp.62-70
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• 2019

The study used cross-lagged path modeling to examine the longitudinal associations between self-esteem and community spirit among adolescents. This is a longitudinal study designed to examine the developmental changes of adolescents' self-esteem and community spirit in Korea. This study used the data collected by the Korean Children and Youth Panel Survey (KCYPS) from 2014 through 2016. Participants were surveyed from the 5^th grade to the 7^th, which belonged to the 1^st elementary school cohort panel of the KCYPS. To be used as the data of this study, children should have all information at 3-time points: the 5^th grade; 6^th grade; 7^th grade. The collected data were analyzed with PSAW 18.0 and AMOS statistical program. The participants in this study were 903 males (51.6%) and 847 females (48.4%). The level of self-esteem was 3.29±.51, 3.19±.55, and 3.15±.57 point at 5^th grade, 6^th grade, and 7^th grade each. The level of community spirit was 3.12±.52, 3.09±.59, 3.15±.55 point respectively. Community spirit from elementary school to middle school is consistently predicted by previous self-esteem. Likewise self-esteem has a significant predictive effect on subsequent community spirit.

• Korean Journal of Social Welfare Studies
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• v.48 no.4
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• pp.157-185
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• 2017

This study aimed to explore the trajectories of economic preparations for the aging among people with physical disabilities and to identify the determinants according to the Andersen model. For this study, data were drawn from Panel Survey of Employment for the Disabled (PSED). A total of 1,847 samples were used from the second to the eighth wave. Latent class growth model was conducted to explore the longitudinal change classes for the disabled, and the multinominal logistic regression analysis was conducted to examine the influence of the determinants. As a result, four classes were identified: preparation decrease group, continuous non-preparation group, preparation increase group, and continuous preparation group. Each group was found to be associated deferentially with education level, family income, socioeconomic status, employment, home ownership, national basic livelihood security recipient status, and ADL. These findings proposed the practical and political implications for the strategies concerned with facilitating the economic preparations for the aging among the disabled.

• Korean Journal of School Psychology
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• v.9 no.2
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• pp.289-309
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• 2012

This is a longitudinal study which analyzed suppression effects of active/passive coping strategies on academic burnout, using a structural equation modeling. A total of 357 middle school students participated in this study for two waves. In order to measure the levels of students' coping strategies and academic burnout, the Ways of Coping Checklist and the Korean version of Maslach Burnout InventoryStudent Survey(MBI-SS) were used. Latent variables were constructed with standardized residuals computed from a simple linear regression in order to capture the intra-individual changes between two time points. The results of this study are like below. First, the relationship between the change of active coping strategy and the change of passive coping strategy is positively and significantly related with each other. This result indicates that students under stress use various coping strategies simultaneously. Second, significant suppression effects were revealed between the change of active coping strategy and the change of passive coping strategy. That is, when controlling passive coping strategy, the negative relationship between the change of active coping strategy and the change of academic burnout increased. On the other hand, when controlling active coping strategy, the positive relationship between the change of passive coping strategy and the change of academic burnout increased. Based on these results, the value of this study and implications for counseling were discussed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.971-979
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• 2023

Small ships (<499 GT) constitute 46% of the existing ships, therefore, it can be concluded that they produce relatively high CO₂ gas emissions. Operating in optimal trim conditions can reduce the resistance of the ship, which results in fewer greenhouse gases. An affordable way for trim optimization is to adjust the weight distribution to obtain an optimum longitudinal center of gravity (LCG). Therefore, in this study, the effect of LCG changes on the resistance of a small planing ship is studied using empirical and numerical analyses. The Savitsky method employing Maxsurf resistance and the STAR-CCM+ commercial computational fluid dynamics (CFD) software is used for the empirical and numerical analyses, respectively. Finally, the total resistance from the ship design process is compared to obtain the optimum LCG. To summarize, using numerical analysis, optimum LCG is achieved at the 46.2% length overall (LoA) at Froude Number 0.56, and 43.4% LoA at Froude Number 0.63, which provides a significant resistance reduction of 41.12 - 45.16% compared to the reference point at 29.2% LoA.

• The korean journal of orthodontics
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• v.40 no.6
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• pp.398-410
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• 2010

Objective: The purpose of this study was to investigate the changes in dentofacial morphology of non-orthodontically treated female patients with TMJ disk displacement. Methods: The sample consisted of 25 Korean female patients with bilateral TMJ disk displacement who visited the Department of Orthodontics, Seoul National University Dental Hospital from 1996 to 2006. Disk displacements were diagnosed using the magnetic resonance imaging (MRI) of both TMJs. Baseline (T1) and follow-up (T2) lateral cephalograms were analyzed. The mean age of samples at T1 was $18.1{\pm}3.5$ years (range 14.2 - 25.8 years) and at T2, $21.1{\pm}3.5$ years (range 16.2 - 28.0 years). The mean observation period was $3.0{\pm}1.9$ years. Descriptive statistics for each variable were calculated at baseline (T1) and follow-up (T2) stages, and during the observation period (T2-T1). Results: Skeletal changes were found in 64% of the non-orthodontically treated female patients with TMJ disk displacement during the observation period. The L1 to Mandibular plane distance (mm) increased significantly by 0.8 mm (p < 0.01). But there were no significant differences in the other dental relationship variables (overjet, overbite, U1 to palatal plane) during the observation period. Most patients with skeletal changes showed a backward rotation of the mandible. The ratio of the rotation was a decrease of SNB by $0.43^{\circ}$ for every $1^{\circ}$ increase of FMA (Spearman rho = -0.660, P < 0.01). A few patients showed a distal shift of the mandible without rotation or significant changes in the vertical dimension. Conclusions: During observation periods without orthodontic treatment, non-growing patients with TMJ disk displacement showed dentoskeletal changes, mainly backward rotation of the mandible.